All is not lost when a batch of beer is spotted that may eventually be ascribed with the scarlet letter “A” for astringency. The key with this statement is that the beer is identified and slated for corrective actions before you end up with a palate-puckering bottle or keg of astringent alt. The good news is that there are numerous cures to astringency, and they all begin with understanding the root cause.
Astringency is a mouthfeel associated with tannins, and is commonly found in tea, young red wine, really hoppy beers, especially dry hopped brews, and grainy and unbalanced beers. Tea astringency can be rectified with milk. Wine astringency can be reduced with egg white finings. And beer astringency can be associated with haze in finished beer. The common element of these three examples is reaction with proteins. Tea tannins react with milk proteins, wine tannins react with egg proteins, and hop tannins react with malt proteins to form haze. And tannins bind with proteins in the mouth to cause that unpleasant texture associated with astringent foods and beverages.
The solution to astringency is protein-tannin interaction. The general idea is to get those tannins that will, given the chance, assault your palate to embrace another protein and gracefully exit the scene before you keg or bottle your beer. Cold temperature also helps with this process and explains why aged lagers are rounder than young lagers. Things you can use at home to combat your astringent alt include PVPP (a protein analog), cold aging, isinglass, egg whites, and time.